As shown in FIG. 25A, a prior contact device 1000 includes a sealed receptacle 1100 (see Japanese patent laid-open publication No. 10-326530). In the following explanation, an upper direction in FIG. 25A denotes a forward direction of the contact device 1000, and a lower direction in FIG. 25A denotes a rearward direction of the contact device 1000.
The sealed receptacle 1100 includes a contact case 1110 made of dielectric materials, a cylindrical member 1120 made of metals, and a closure plate 1130. The contact case 1110 is provided in its rear wall with an aperture 1111. The cylindrical member 1120 has its front end secured in an airtight manner to a periphery of the aperture 1111 of the contact case 1110. The closure plate 1130 is secured in an airtight manner to a rear end of the cylindrical member 1120. The sealed receptacle 1100 houses fixed contacts 1200 and a movable contact 1300.
The contact device 1000 further includes a drive device 1500 having a shaft 1400. The shaft 1400 has its front end attached to a holding case 1600. The holding case 1600 holds the movable contact 1300 movably along the forward/rearward direction. In addition, the holding case 1600 accommodates a contact pressure provision spring 1700. The contact pressure provision spring 1700 biases the movable contact 1300 forward such that the movable contact 1300 comes into contact with the fixed contacts 1200 at a desired contact pressure. The drive device 1500 moves forward/rearward the shaft 1400 by use of an electric magnet. The movable contact 1300 is kept away from the fixed contacts 1200 when the shaft 1400 is moved rearward by a predetermined distance. The movable contact 1300 comes into contact with the fixed contacts 1200 when the shaft 1400 is moved forward by a predetermined distance.
The sealed receptacle 1100 further houses an arc protection member 1140. As shown in FIG. 25B, the arc protection member 1140 includes a peripheral wall 1141 shaped into a cylindrical shape and a flange 1142. The peripheral wall 1141 is configured to conceal a junction between the contact case 1110 and the cylindrical member 1120 from the fixed contacts 1200 and the movable contact 1300. The arc protection member 1140 is pressed forward by pressing springs 11150 such that the flange 1142 comes into contact with the cylindrical member 1120. Thereby, the arc protection member 1140 is held in a predetermined position in the sealed receptacle 1100.
As apparent from the above, the prior contact device 1000 needs the pressing spring 1150 to hold the arc protection member 1140.